NOISES OF INSECTS. 



307 



ments of the sound, which accordingly he found to cease 

 entirely when they were stopped with gum, though while the 

 wings were in vibration. Pursuing his researches, he ex- 

 tracted one of these spiracles, and opening it carefully, found 

 its posterior and inner lip, which is directed towards the 

 commencement of the trachea, to be expanded into a small 

 flat crescent-shaped plate, upon which are nine parallel very 

 delicate horny laminae, the central one being the largest, 

 while those on each side became gradually smaller and lower ; 

 and it is, he is persuaded, in consequence of the air being 

 forcibly driven out of the trachea and touching these laminae 

 that they are made to vibrate and sound precisely in the same 

 way with the glottis of the larynx. Dr. Burmeister (who 

 remarks that Chabrier in his Essai sur le Vol des Insectes, 

 p. 45, &c, has also explained the hum of insects as produced 

 by the air streaming from the thorax during flight, and also 

 speaks of lamina? which lie at the aperture of the spiracle), 

 in order to be certain that the lamina? in question in the 

 posterior spiracles of the thorax are alone concerned in pro- 

 ducing sound, also inspected the anterior ones, but without 

 finding in them any trace of these lamina?. He explains the 

 weaker and sharper tones produced when the wings all 

 but the very roots are cut off as resulting from the weaker 

 vibrations of the contracting muscles, and consequent less 

 forcible expulsion of the air when the vibratory organs are 

 removed; and he thinks with Chabrier that some air may 

 escape through the open trachea of the wings which are cut 

 off. Though he regards these laminae as the cause of hum- 

 ming in bees and flies, he does not decide that other causes 

 may not produce the buzz of cock-chafers, &c, in the thoracic 

 spiracles of which he could not discern them. 1 



Aristophanes, in his Clouds, deriding Socrates, introduces 

 Chaerephon as asking that philosopher whether gnats made 

 their buzz with their mouth or their tail. 2 Upon which 

 Mouffet very gravely observes, that the sound of one of these 

 insects approaching is much more acute than that of one 

 retiring ; from whence he very sapiently concludes, that not 



1 Burmeister, Manual of Ent. 468 — 470. 



2 Act i. Sc. 2. 



x 2 



